1. Field of the Invention
The present invention relates to an ink-jet recording process and more particularly to an ink-jet recording process carried out by using a plural number of color inks.
2. Description of the Prior Art
Heretofore, in multicolor or full-color recording by the ink-jet recording process, various proposals have been made for the purpose of obtaining colored picture images of high quality. Among them, there have been proposed recording processes in which n ("n" represents an integer of 2 or more) kinds of inks which differ from one another in dye concentration are employed for one color for the purpose of obtaining colored picture images having high reflection density (optical density, hereinafter simply referred to as "O.D."), wide range of color-reproducibility and excellent gradient (See, for example, Japanese Patent Laid-Open No. 156264/1982).
However, even when ink-jet recording is carried out by using the inks prepared from one dye, the hue reproduced by each of the inks varies in compliance with the dye concentration. Therefore, when gradation in one color is pursued, the variation in the hue becomes discontinuous.
In particular, in the full-color recording, the hues of the primary colors as used (yellow, magenta and cyan) vary discontinuously upon gradation expression, which makes the picture designing extremely difficult. Alternatively one may also consider to correct color deviations by masking, but there remains a disadvantage that production costs are increased because of the complicatedness of the picture processing and the increments of electric circuits resulting from the increase in parameters to be corrected in proportion to the number of inks.
FIG. 1 is a Hunter's chromaticity diagram of recorded matters as expressed analogically by the gradation expression by using the inks of the following composition. Recording is carried out by the drop-on-demand type ink-jet recording process, and the gradation expression is obtained by varying the dot size.
______________________________________ Ink No. 1 (Composition) ______________________________________ Acid Red 94 2 parts by weight Water 48 parts by weight Ethylene glycol 24 parts by weight Glycerol 24 parts by weight Triethanolamine 1.9 parts by weight Surfactant (trade name: 0.1 parts by weight Emal NC; mfd. by Kao Soap Co., Ltd.) ______________________________________
______________________________________ Ink No. 2 (Composition) ______________________________________ Acid Red 94 0.7 parts by weight Water 49.3 parts by weight Ethylene glycol 24 parts by weight Glycerol 24 parts by weight Triethanolamine 1.9 parts by weight Surfactant 0.1 parts by weight (trade name: Emal NC; mfd. by Kao Soap Co., Ltd.) ______________________________________
FIG. 2 shows the resulting measured values of O.D. of the above recorded matters. As can be seen from FIG. 2, there are obtained recorded matters in which O.D. values vary continuously and are reproduced over a wide range by using Ink No. 1 and Ink No. 2 respectively, according to the O.D. range reproduced by itself. On the other hand, as can be seen from FIG. 1, when the gradation expression as shown in FIG. 2 is performed, the hues reproduced by Ink No. 1 and Ink No. 2 do not correspond with the continuity of the gradation expression. Therefore, the variation in the hue becomes discontinuous, and color deviation occurs.